The present invention relates to devices for packaging selected items. More particularly, the present invention relates to a packaging device for continuously packaging selected items in a negative pressure environment.
Conventional devices for continuously sealing containers containing selected items, and in particular, selected food items, have generally not included any provision for creating a slight negative pressure within the sealed container. Generally, such continuous packaging devices have utilized moving heat sealing heads to engage a covering material to the container to seal the container. The resulting sealed container thus has atmospheric pressure within it. This type of sealed container has normally been acceptable to consumers. However, with a wider variety of food items being packaged in containers having a flexible covering material applied by heat sealing head, certain problems have arisen in this type of packaging configuration.
In particular, it is desirable to retort or heat these type of sealed containers when they contain certain types of food items after the containers have been sealed. With certain types of food items, the retorting process can free gases trapped within the material sealed within the container. This freeing of gases during the retorting process can increase the pressure within the sealed container. This increase in pressure within the sealed container can then result in the flexible covering material flexing upwardly somewhat to create a convex or domed configuration.
From a consumer standpoint, the domed configuration of the lid of sealed containers holding food items is undesirable. It is a common misconception by consumers that a domed appearance in a sealed package with a flexible lid indicates that the food item within the sealed container may be unsuitable for human consumption. Although this assumption is normally incorrect, it would be desirable to provide a packaging device which would be capable of sealing a container having a food item with a flexible sealing cover such that a slight negative pressure exists within the sealed container. Then, during a retorting process of the container, any release of gases by the product within the containers would not result in a doming of the flexible sealing cover. It would be particularly advantageous to provide for the slight negative pressure within the sealed container solely by mechanical means, and without any delay or adjustment of the production rate of the packaging machine.
It is therefore one object to the present invention to provide a packaging device that is capable of producing a sealed container with at least a slight negative pressure within the container.
Another object of the present invention is to provide a packaging device that is capable of producing a sealed container with a negative pressure within the container solely by mechanical manipulation of the container.
Yet another object of the present invention is to provide a packaging device that is capable of producing a sealed container with a negative pressure by mechanical manipulation of the container while the containers are moving in a continuous manner.
According to the present invention, a packaging device for sealing a container with a covering material is provided. The device includes means for conveying the container from a filling location to a sealing location. Means are provided for mating the covering material with the container opening to seal the container while the container is continuously moving. In addition, means for reducing temporarily the volume of the container prior to mating the covering material with the container opening are provided to reduce somewhat the pressure within the container after it is sealed.
One feature of the foregoing structure is that means for reducing temporarily the volume of the container are provided. One advantage of this feature is that, after the container is sealed, a slight negative pressure exists within the sealed container.
In preferred embodiments of the present invention, the volume reducing means includes means for deforming temporarily a portion of the container such that the volume of the container is reduced. One advantage of this feature is that the resulting negative pressure within the sealed container is created solely be mechanical manipulation of the container.
Also in preferred embodiments of the present invention, the deforming means includes a lifting assembly which lifts and deforms a bottom portion of the container a distance sufficient to reduce the volume of the container prior to sealing. The reduction in volume of the container is in an amount sufficient to create a negative pressure in the container after the container is sealed and the lifting assembly is disengaged from the container. One advantage of this feature is that, after the sealing is completed, the container is returned to its normal configuration.
Applicants' device is thus capable of packaging a selected item in a sealed container such that a slight negative pressure exists within that sealed container. Applicants' device is capable of continuously conveying the containers along a selected path such that the process is accomplished at a commercially acceptable rate of production. The slight negative pressure with the sealed container is accomplished by temporarily mechanically deforming the container just prior to the sealing process such that the volume within the container is reduced somewhat. After the container has been sealed, the mechanical deformation of the container is eliminated, and the container assumes its normal configuration, which then results in a slight negative pressure within the sealed container. This provides for a slight negative pressure within the container without any intrusion into the container or any interference with the product within that container.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.